The present invention relates to a motion control device of vehicles, such as an automobile, and particularly, to a motion control device which controls the motion of a vehicle at the time of turning manipulation.
Conventionally, a motion control device including a braking force control device which controls a vehicle braking force so that an actual turning controlling variable becomes a target turning controlling variable is widely known as a kind of motion control device which controls the motion of a vehicle at the time of turning manipulation. In this braking force control device for vehicle stabilization control, at the time of turning manipulation of a vehicle, braking forces applied to right and left steered wheels are individually controlled so as to minimize, for example, the deviation of an actual yaw rate based on an actual steering state of the steered wheels from a target yaw rate based on the steering angle and steering speed of a steering wheel by a driver. For example, for vehicle stabilization control, a system referred to as a so-called dynamic stability control (hereinafter appropriately abbreviated as “DSC”) system which is adapted to perform the automatic control of a wheel braking force or the automatic control of engine output in addition to this is also a kind of such a braking force control system.
Additionally, in recent years, in addition to this braking force control, a steering angle control device which controls the steering angle of the steered wheels so that an actual turning controlling variable becomes a target turning controlling variable with respect to the steering angle control of the steered wheels is also put to practical use. In such a steering angle control device, the steering angle of the steered wheels is controlled so as to minimize, for example, the deviation of the actual yaw rate from the target yaw rate at the time of turning manipulation of a vehicle, and thereby, the steering of a driver is assisted. For example, a so-called steering stability control (hereinafter appropriately abbreviated as “SSC”) system is also a kind of steering angle control system.
It is usual to minimize any deviation, which cannot be eliminated only by the automatic control of a steering angle, first, by automatically controlling the steering angle of steered wheels, in a case where the deviation (for example, yaw rate deviation) of the actual turning controlling variable from the target turning controlling variable is small, so that an actual turning controlling variable becomes a target turning controlling variable by the steering angle control in a case where the motion control of a vehicle at the time of turning manipulation is performed by combining the above-described steering angle control with the aforementioned braking force control, and by using the braking force control system concurrently and automatically controlling the braking force to each wheel in a case where the deviation (for example, yaw rate deviation) of the actual turning controlling variable from the target turning controlling variable exceeds the operation limit of the steering angle control system (for example, refer to JP-A-3-227762).
In a vehicle including the motion control device which performs the motion control of the vehicle at the time of turning manipulation by combining the steering angle control and the braking force control as described above, in a case where so-called oversteering has occurred at the time of turning manipulation, the steering of a driver is assisted by only the steering angle control from a normal region to a region where the compensation quantity of the yaw moment is relatively small. When the yaw rate deviation becomes large with the progress of the oversteering, and exceeds the operation limit of the steering angle control system, the braking force control system is used together. In this state, however, even if the driver has performed K-turn manipulation, etc. of a steering wheel in order to eliminate or suppress oversteering, since the steering angle control system cooperates with the braking force control system, the behavior of the vehicle does not necessarily respond to the steering wheel manipulation of the driver faithfully, and the driver may feel the sense of incompatibility. Additionally, since both systems are used together, there is a difficulty that the convergence of control when the braking force control is completed is not good.